— 132 — 



metre. This sand is more closely covered with vegetation 

 than the clay, and two species are specially characteristic: 

 Carex physodes (the aerial parts withered, but fresh buds 

 present far down in the dense mat of old sheaths) and Arte- 

 misia herba alba (a form of A. maritima s. lat.); the Carex is 

 restricted to the sand-patches, the Artemisia occurs now and 

 then on the bare clay. The following species likewise follow 

 the sand: Haloxylon Ammodendron, small shrubs about 0,6 — 1 

 metre high, Salsola sogdiana, Halimocnemis villosa, Halanthium 

 gamocarpum, Cousinia dichotoma. Halimocnemis and Halan- 

 thium are grey annual Chenopodiaceae (leaf-succulents) never 

 found on deep dry sand; they are typical clay-plants, and 

 along with the other plants mentioned, they occur here 

 chiefly on the sand because it only formed a thin layer and 

 thus created more favourable conditions by protecting the 

 firm subsoil from desiccation (see above p. 80). 



There is a relation between the presence of the sand in 

 this place and Carex physodes. It is very improbable that 

 this sedge could originally have grown on the clay-surface 

 and thus have caused the sand to become fixed. I never 

 found it on clay, nor has any one else so far as I know, 

 and it would not be in accordance with its mode of growth. 

 The sand must have been present first, perhaps retained by 

 stems of clay-plants, and then Carex physodes appeared — 

 its vesicular spathes are easily transported — the stability 

 of the sand being assured by its presence. More extensive 

 investigations may perhaps decide this question, but my 

 observations in this locality were very limited. 



9. Desert at Dana Sher Kala ("the castle of the wide- 

 awake tiger") on the left bank of the Amu Darya. June 27. 

 1899. This locality (see also p. 76) lies west of the river, 

 like Kara Aigir (No. 8) and the locality described next (No. 

 10), so that there is very little sand. The desert is a stony, 

 gravelly plain (coarse sand and small stones) with an exceed- 

 ingly poor vegetation. The only species is Salsola rigida as 

 small scattered shrubs with little heaps of sand round the 

 base — a sign of sand-drift, but the sand does not remain 

 lying. In one small valley, sand had accumulated and the 



